In recent years, the wiring of printed circuit boards (PCBs) has gradually progressed towards high-density integration and thinning. With the thinning of the substrate, under high-temperature processes, the substrate is easier to warp. At this time, it is preferred that the coefficient of thermal expansion of resin used in an insulating layer is similar to that of the wafer. However, the coefficient of thermal expansion of general insulating resin is high. Therefore, development of insulating resin with a low coefficient of thermal expansion is desirable.